In recent years, as environmental problems such as global warming emerge, regulations for exhaust gas have been tightened, in particular, emissions of exhaust gas of a vehicle have been strictly controlled.
In detailer, according to EURO-6, in the case of a diesel engine for a car, emissions of NOx need to be reduced to about 80 mg/km. In response, automobile industries have used new technologies such as exhaust gas recirculation (EGR), LNT, and SCR.
The EGR apparatus may include a high pressure exhaust gas recirculation (HP-EGR) apparatus that re-circulates exhaust gas and mixes the re-circulated exhaust gas with compressed air and a low pressure exhaust gas recirculation (LP-EGR) apparatus that re-circulates exhaust gas of a back end of a diesel particle filter (DPF) and mixes the re-circulated exhaust gas with air at a front end of a turbocharger.
In this case, to cool the re-circulated exhaust gas, an exhaust gas recirculation line is provided with an EGR cooler that is made of a stainless material having a high corrode resistance against a high temperature state and condensed water.
By the way, the EGR cooler made of the stainless material is heavy, has low heat transfer efficiency and poor moldability, and is expensive in the overall cost of parts. Therefore, researches for an EGR cooler made of an aluminum material that has high heat transfer efficiency and good moldability and is relatively inexpensive in the cost of part have been conducted.
In the EGR cooler made of an aluminum material, a heat exchange member, or the like is made of aluminum and is relatively vulnerable to heat over an SUS material and when coolant bubble is generated inside a cooler, cooling performance deteriorates, a thermal deformation occurs, and a coolant is leaked to damage an engine.
FIG. 3 is a perspective view of a typical water-cooled EGR cooler.
Referring to FIG. 3, an inlet and an outlet of a lower portion of the EGR cooler 100 are each provided with a coolant supply pipe 104 and a coolant exhaust pipe 115 and an inlet cone part is provided with a bypass valve 400. Further, an actuator 405 that actuates the bypass valve 400 is disposed.
In this configuration, the coolant is supplied to one side of the lower portion and discharged to the other side of the lower portion, such that bubbles formed due to a boiling of the coolant may not be smoothly discharged.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this field to a person of ordinary skill in the art.
The document Korean Patent Laid-Open Publication No. 10/2014/0000406 discloses subject matter that is related to subject matter described herein.